\begin{tikzpicture}
	\pgfmathsetmacro{\r}{2}
	\tkzDefPoints{0/0/O, \r/0/B}
	\tkzDefPoint(165:\r){A}
	\tkzDefPoint(90:\r){D}
	\tkzDefPoint(75:\r){C}

	\tkzDrawSegments(O,A  O,B  O,C  O,D)
	\tkzMarkRightAngle(B,O,D)
	\tkzMarkRightAngle[size=0.4](A,O,C)
	\tkzLabelPoints[below](A, O, B)
	\tkzLabelPoints[right](C)
	\tkzLabelPoints[left](D)
\end{tikzpicture}

